As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF AT 800 AGL AFT LAV SMOKE MESSAGE, NO VISIBLE SMOKE OR SMELL. CREW DECLARED EMERGENCY AND RETURNED TO FIELD, TRUCKS ROLLED, NO BRACE AND NO OVER WEIGHT LANDING. THE PLANE TAXIED TO GATE UNDER ITS OWN POWER NO INJURIES. SMOKE AFT LAV WNG AFTER TAKE OFF / REMOVED AND REPLACED AFT LAV SMOKE DETECTOR IAW CRJ 900 AMM 26-16-01-000/400-801-A01-PSA. OPS CHECK GOOD."